Apparatus for maintaining proper depth correlation in well logging apparatus



Sept. 26, 1961 J. L. CLEVELAND 3,001,396

APPARATUS FOR MAINTAINING PROPER DEPTH CORRELATION IN WELL LOGGING APPARATUS Filed Feb. 14, 1958 3,001,396 APPARATUS FOR MAINTAINING PROPER DEPTH CORRELATION IN WELL LOGGING APPARATUS James L. Cleveland, 277 Boulevard, Scarsdale, N.Y. Filed Feb. 14, 1958, Ser. No. 715,381 4 Claims. (Cl. 73-152) This invention relates generally to conducting operations in a subterranean drill hole and more particularly to a system for conducting such operations with instruments suspended from a floating structure such as a shi or barge.

Currently the successful completion of increasing numbers of offshore wells has encouraged producers to exi tend their operations to prospective new fields located at greater distances from the short and consequently in deeper water. The depth of the water at these new locations precludes the use of conventional drilling methods. A new technique of drilling from a floating structure has presented the drillers with new problems which were not encountered when drilling from fixed platforms. The present invention, although not directed to drilling operations, concerns itself with two of these problems, namely, movement of the floating structure with respect to the bottom of the water, and the guiding of the drill stem and/or the well casing into the mouth of the subterranean drill hole. The drillers overcame the first of these two problems by using a drill stern having a kelly bar of square cross section, or one provided with splines, so that it would slide vertically in the rotary as the ship or barge moves vertically as a result of tide or wave action on it. The second problem was solved by using guide lines that are anchored on the earth and extend upwardly to the floating structure where they pass over pulleys and the free ends provided with weights to maintain them taut. A guide yoke structure was provided adapted for moving up and down along the guide lines.

Wells drilled, as described above, from floating structures often extend downwardly through a number of potentially productive formations; casing is set below the deepest productive formation; and completion is effected by perforating the casing at the formation level. These wells are logged one or more times during and after completing drilling operations and particularly after a deep formation has been exhausted of oil and it is desired to produce from the next deepest productive formation by perforating the casing at that formation.

Perforating and logging instruments are usually enclosed in pressure resistant capsules that are raised and lowered in the drill hole by means of flexible cables. These cables contain the usual electrical conductors and are connected to conventional drawworks indicators, recorders, or control circuits. Obviously, when using these instruments for conducting operations in wells which have been drilled from floating structures, they too must be operated from floating structures.

Since floating structures respond to tide and wave action, their movement would be imparted to any instrument suspended by cable from them. This movement of the instrument with respect to the formations penetrated by the drill hole would make it impossible to perforate casing with any degree of depth accuracy. In fact, it is possible to completely miss the productive formation. Additionally logs made with logging instruments that respond to tide and wave motion would be meaningless since they could not be correlated with the depth of the instrument sensing the parameter that is being measured.

Workers have heretofore attempted to obviate the above difliculties by providing systems for nullifying the motion imparted to the suspended instrument by movement of the floating structure occasioned by waves, tides,

I Patented Sept. 26, 1961 2 etc. Some of these, although relatively complicated and expensive have met with a degree of success. Others have proved to be completely inoperative to accomplish the desired result.

The present invention overcomes the above difliculties by providing a simple economic system for completely nullifying any motion that the floating structure would tend to impart to an instrument suspended therefrom. This is true regardless of whether the instrumentis to be maintained in the drill hole at a fixed position with respect to the formations penetrated by the drill hole or to be moved continuously in the drill hole at a uniform rate with respect to them.

Therefore the primary object of this invention is to provide means for nullifying any motion that a floating structure would impart to an instrument suspended therefrom. Another object of this invention is to provide simple mechanical means operative by the motion of the floating structure for nullifying the effects of waves, tides, etc. on an instrument suspended from the structure. This invention also contemplates means whereby takeup and payout means carried by a floating structure can be operated at a constant uniform speed to move an instrument along a drill hole at a uniform speed with respect to the formations. Still another object of this invention is to provide means whereby the drawworks and recorder can be operated at a uniform speed while a subsurface instrument is moved in a drill hole in one direction at a uniform speed with respect to the formations. Other objects and advantages of the instant invention will become apparent from the following detailed description when taken with the drawing in which the single figure illustrates in vertical elevation, partly in vertical section, a subterranean well operation being conducted from a floating structure.

Although the present invention finds broad application in that it can be used to position an instrument in a subterranean well at a fixed depth and maintain the instrument at that depth, or wherever it is desired to traverse the formations penetrated by a subterranean Well with an instrument at a uniform vertical speed with respect to the formations, regardless of the vertical movement of the floating. structure from which it is suspended, it will be described in detail in connection with a continuous well logging operation.

Referring to the drawings, there is shown schematically earth 10 underlying a body of water 11 on the surface of which is a floating structure 12, such as a barge, ship, or other platform from which subterranean operations may be carried out. In the earth formation 10 there is illustrated a drill hole or well 13. Disposed within the mouth of the drill hole '13 is a well logging instrument 14 that is adapted to traverse the formations of the earth penerated by the well 13. Logging instrument 14 may be any one of the conventional types used for making the various well logs. Instrument 14 is supported by a conventional cable 15 carrying one or more electrical conductors. Cable 15 passes upwardly through an opening 16 in the floating structure and over a sheave 17 and extends to a pay-out take-up drum 1% that is rotatably mounted in a conventional manner on the floating structure 12. It is to be understood that drum 18 is provided with conventional drawworks for rotating it to pay out or take up cable to lower or raise, respectively, the instrument 14 in the drill hole Drum 18 is provided with two or more slip rings 19, the number of which depends upon the number of electrical conductors carried by the cable 15, and the number of parameters that it is desired to log. Slip rings 19 are provided with brushes 20 by means of which electrical signals, transmitted by the conductors in cable 15, can be conducted to'c'on'veutional recording equipment 21, which is also carried by the floating structure 12.

Sheave 17 is supported by a derrick 22, or other means, of conventional construction above the floating structure. If the support for sheave 17 was fixed with respect to the derrick 22, then it would be impossible to raise or lower the surveying instrument in well 13 in a continuous manner at a uniform speed with regard to the formations penetrated by the well. It would obviously have superimposed upon its vertical movement the vertical movement of the floating structure, which would be occasioned by tides, waves or other swells occurring in the water, as described above. As pointed out above, the principal object of the instant invention is to overcome this objectionable feature. This is accomplished by anchoring a weight member 23 on the earth 10, forming the bottom for the body of Water 11 overlying it, and passing a cable 24 from the weight member 23 over a drum-like pulley 25 that is rotatably supported on the floating structure 12. The other end of cable 24 supports a Weight element 26. With such an arrangement, vertical movement of the floating structure with respect to the bottom of the water 11 will produce a proportional, rotational movement of the drum-like pulley 25. This rotational movement of drum-like pulley 25 can be utilized to nullify any vertical movement of the logging instrument 14 in the drill hole 13, such as is occasioned by vertical movement of the floating structure 12 produced by waves, tides, etc. In order to utilize the rotational movement of drum-like pulley 25 to accomplish the end recited immediately above, sheave 17 has interposed between its support and the derrick 22 means whereby it can be raised or lowered with respect to the top of derrick 22. These means may comprise a second sheave 27 rotatably supported by the top of derrick 22 over which a cable 28 from the support of sheave 17 passes to a pay-out take-up drum-like pulley 29. Pulley 29 is mounted coaxially with pulley 25 and adapted to be driven thereby. In order to accurately compensate for vertical movement of the floating structure on which these pulleys are mounted, pulley 25 should be twice the diameter of pulley 29. The end of cable 28 preferably passes around the pulley 29 a number of times and is secured to the pulley so that, when the pulley 29 is rotated by pulley 25, it will take-up or pay-out the cable 28 to raise or lower, respectively, pulley 17.

In order that the portions of cable 15, which extend from both sides of pulley 17, will be parallel, an idler pulley 30 is provided. Pulley 30 may be rotatably mounted in a support 31 carried by the derrick 22. The idler pulley 30 may serve a second function; that of correlating the recorder 21 with the depth of the instrument 14 in the drill hole 13. As shown in the drawing, this is accomplished by causing pulley 30 to actuate the driver unit of a Selsyn system while the driven unit drives the recorder strip take-up roll. This is a conventional way of measuring depth when logging a drill hole. It is important that the portions of cable extending from both sides of pulley 17 be maintained in fixed angular relationship to each other, otherwise, some vertical mo tion would be imparted to the logging instrument by the floating structure. The present invention effects a 100% cancellation of the motion that the floating structure tends to impart to the logging instrument 14. With this novel system, the take-up pay-out drum 18 can be driven at a uniform speed to continuously move the logging instrument up or down in the drill hole at a uniform speed with respect to the formations penerated by the well.

Although the instant invention has been described in detail, as applied to well logging, it finds equal application in completing wells by perforating the casing. The logging instrument 14 need only be replaced by a gun perforator and the recorder 21 by firing control circuits. The gun perforator can be lowered in the drill hole to any desired depth and maintained at that depth fixed with respect to the potentially productive formation while perforating the casing.

I claim:

1. An apparatus for movably supporting an instrument in an off-shore drill hole in the earth from a floating structure that moves vertically in response to wave and tide action, which apparatus comprises a sheave supported on said floating structure in a position adjustable along a predetermined path, a pay-out take-up drum r0- tatably mounted on said structure, means for suspending the instrument in the drill hole and effecting a controlled movement thereof including cable means attached to the instrument and extending therefrom over said sheave to said drum for movement in response to rotation of the latter and means for maintaining those portions of the cable adjacent said sheave on both sides thereof at a constant angularity to each other and said predetermined path, an element movably supported on said floating structure, second cable means anchored to the earth and connected to said element to move it in response to movement of said structure and in direct proportion thereto, and means responsive to movement of said element to adjust the position of said sheave along said path an amount equal to one-half the movement of said structure and in a direction to avoid movement of the instrument in response to such movement of the structure.

2. An apparatus for movably supporting an instrument in an off-shore drill hole in the earth from a floating structure that moves vertically in response to wave and tide action, which apparatus comprises a sheave supported on said floating structure in a position adjustable along a predetermined path, a pay-out take-up drum rotatably mounted on said structure, means for suspending the instrument in the drill hole and effecting a controlled movement thereof including cable means attached to the instrument and extending therefrom over said sheave to said drum for movement in response to rotation of the latter and arranged with those portions of the cable adjacent said sheave on both sides thereof being parallel with each other and said predetermined path, an element movably supported on said floating structure, second cable means anchored to the earth and connected to said element to move it in response to movement of said structure and in direct proportion thereto, and means responsive to movement of said element to adjust the position of said sheave along said path an amount equal to one-half the movement of said structure and in a direction to avoid movement of the instrument in response to such movement of the structure.

3. An apparatus for movably supporting an instrument in an off-shore drill hole in the earth from a floating structure that moves vertically in response to wave and tide action, which apparatus comprises a sheave supported on said floating structure in a vertically adjust able position over the drill hole, a pay-out take-up drum rotatably mounted on said structure, means for suspending the instrument in the drill hole and effecting movement thereof including a cable supplied from said payout take-up drum and extending over said sheave and thence vertically to an attachment to the instrument and means for maintaining vertical a portion of said cable adjacent said sheave on the drum side, an element movably supported on said floating structure, a second cable an chored to the earth and connected to said element to move it in response to movement of said structure and in direct proportion thereto, and means responsive to movement of said element to adjust the Vertical position of said sheave by an amount equal to one-half the movement of said structure and in a direction to avoid movement of said instrument in response to such movement of the structure.

4. An apparatus for movably supporting an instrument in an off-shore drill hole in the earth from a floating structure that moves vertically in response to wave and tide action, which apparatus comprises a first sheave, means for supporting said first sheave on said structure in a vertically adjustable position over the drill hole, a pay-out take-up drum rotatably mounted on said structure, means for suspending the instrument in the drill hole and effecting movement thereof including a first cable supplied from said pay-out take-up drum and extending over said first sheave and thence vertically to an attachment to the instrument and a pulley guiding said first cable between said drum and first sheave and positioned on said structure so that the portion of the cable between said pulley and sheave is also vertical; said means for supporting said first sheave comprising a first drum-like pulley rotatably mounted on said structure, a second cable anchored to the earth and connected to said first drum-like pulley to rotate it in response to and indirect proportion to the vertical movement of said structure, a second sheave mounted on saidstructure directly over the first sheave, a second drum-like pulley on said structure having a third cable supplied therefrom and extending over said second sheave and attached to said first sheave tosupport it, said second drum-like pulley being connected to the first drum-like pulley for rotation therewith in a relationship such that the third cable is moved to adjust the vertical position of the first sheave by an amount equal to one-half the movement of said structure and in a direction to avoid movement of the instrument in response to such movement of the structure.

References Cited in the file of this patent UNITED STATES PATENTS Broussard Sept. 23, 1958 

